1. Field of the Invention
The present invention relates to a wireless communication apparatus which performs media access control and, more particularly, to access control for improving Quality of Service (QoS).
2. Description of the Related Art
MAC (Media Access Control) is control for causing a plurality of communication apparatuses which perform communication while sharing the same medium to decide how to use the medium in transmitting communication data. Owing to media access control, even if two or more communication apparatuses transmit communication data by using the same medium at the same time, there is less chance of the occurrence of a phenomenon (collision) in which a communication apparatus on the receiving side cannot decode communication data. Media access control is also a technique for controlling access from communication apparatuses to a medium so as to minimize the chance of the occurrence of a phenomenon in which, despite the presence of communication apparatuses having transmission requests, the medium is not used by any of the communication apparatuses.
In addition, several access control techniques designed to improve Quality of Service (QoS) are also known. For example, there is available HCCA (HCF Controlled Channel Access) which is an extended technique of a conventional polling sequence and is used as a QoS technique of guaranteeing parameters such as a designated bandwidth and delay time. In HCCA, scheduling is performed in consideration of required quality in the polling sequence so as to guarantee parameters such as a designated bandwidth and delay time.
Jpn. Pat. Appln. KOKAI Publication No. 2002-314546 discloses a method of assigning priorities to communications between wireless network stations, while referring to QoS in the IEEE 802.11e standard.
An HC according to the IEEE 802.11e contains a scheduling processor which controls transmission of a polling frame to a QSTA and the transmission timings of downlink data. To satisfy the quality of service required by using TS (Traffic Stream) setup from a QSTA, the scheduling processor transmits a polling frame or data for each priority.
If it is necessary to transmit data to a certain QSTA in response to a request from the internal scheduling processor of the HC, it is possible to store a frame in a subqueue for retransmission by using the destination and priority as keys, and transmit the frame as a MAC super frame. It is also possible to store frames addressed to the same destination and having a plurality of priorities into one subqueue, and transmit the frames as a MAC super frame. However, this complicates the process of performing sliding window control for each priority by using a Partial Ack response from the destination terminal. In some cases, the internal process ability of the apparatus may decrease.